For lighting, 10 W fluorescent lamps also at 24 V DC will be used, because they are available from a local retailer along with their replacement tubes – availability is an essential criterion of choice in remote areas with poor access to supplies. They are U-shaped fluorescent lamps (double PL) with an efficiency of 60 lm/W, which is correct for the requirement (see Section 5.2.2).
For ventilation, that essential standby in hot countries, a ceiling fan with large blades, driven by a DC motor with a speed regulator, is chosen. Its nominal power is 20 W and its likely use is 6 h/day.
The television set runs on 12 V DC and only consumes 60 W. If it is decided that the PV system should be 24 V DC, which is likely, a step-down converter 24 V-12 V DC will be needed, and the consumption of 60 W will be increased because of the 80% efficiency of the converter (see Section 5.1.3). This correction will therefore be introduced from the beginning (Table 5.25).
The refrigerator is chosen for its low consumption, with a compressor running on 24 V DC and with reinforced insulation for the storage compartment to reduce energy loss (see Section 5.2.3). Its electrical consumption is estimated at 500 Wh/day.
The power tool running on 230 V AC at a power of 500 W obviously needs an inverter to operate, and its efficiency will need to be taken into account. A sine wave inverter is selected so that the motor does not overheat, and the computer can also be supplied from it.